Optical sensors using chaotic correlation fiber loop ring down

Abstract

We have proposed a novel optical sensor scheme based on chaotic correlation fiber loop ring down (CCFLRD). In contrast to the well-known FLRD spectroscopy, where pulsed laser is injected to fiber loop and ring down time is measured, the proposed CCFLRD uses a chaotic laser to drive a fiber loop and measures autocorrelation coefficient ring down time of chaotic laser. The fundamental difference enables us to avoid using long fiber loop as required in pulsed FLRD, and thus generates higher sensitivity. A strain sensor has been developed to validate the CCFLRD concept. Theoretical and experiment results demonstrate that the proposed method is able to enhance sensitivity by more than two orders of magnitude comparing to the existing FLRD method. We believe the proposed method could find great potential applications for chemical, medical, and physical sensing.

A Brief Review of New Fiber Microsphere Geometries

“…This new type of laser appeared during the last decade, and presents attractive advantages over other lasers, viz. simple technology, low production cost [11], light weight, and immunity to light source oscillations [12]. These features allowed for developments in multiple areas, and applications include fiber and nonlinear optics, laser physics [11], secure optical communications [13], random number generation [14], fiber fault detection [15][16][17][18][19], and sensing [20][21][22].…”

“…For sensing, optical random signals were used for compressive sensing [22]. An improved alternative to the well-known fiber cavity ring down technique was also proposed using random signals, creating a random correlation fiber loop ring down [12]. Random correlation was revealed to be a powerful tool to analyze more complicated systems where traditional interrogation techniques cannot be applied [18].…”

“…Using the abovementioned setup, the spectra of both microspheres presented multiple lasing lines in the region of highest gain of the erbium profile, as visible in the output of Figures 5 and 6. The multiple lasing lines also change in time, due to the modes' competition for gain [12,24].…”

Bunimovich Stadium-Like Resonator for Randomized Fiber Laser Operation

“…This means that, while in conventional lasers the optical modes and their frequency are determined by the optical cavity, in random lasers the modes are determined, with a specific frequency and bandwidth, by the interference of multiple scattering [3]. When gain is applied, random modes will selectively lase in space and time, due to the modes' competition for gain [4,5]. Random lasers present some advantages over other lasers, including low production costs and simple technical design [6,7].…”

“…Random lasers can be engineered to provide low spatial coherence, making them better candidates than conventional lasers for applications in speckle-free imaging and medical diagnosis [10][11][12]. Multiple scattering has been observed using a wide variety of disordered gain materials, including scattering powders [13], zinc oxide nanoparticles [14], microcavities with decoupled gain and scattering regions [5], cold atoms [15], and all-fiber gain media, such as D-shape cross section multimode fiber [16], Er-doped single-mode fibers with randomly distributed Bragg gratings [17], and organic nanofibers [18].…”